The Student Room Group
Reply 1
Its kinda like you start with an 8 by 8 square.
But one side is folded in which makes a triangle at one corner.
The shape is made up of the original square which you found the info already.

A triangle cut out from the top left hand corner.
Notice its mass has been removed from the original square so this gives -8m.
The centre of mass of this triangle is calculated.

The other same triangle is placed onto the square with it NEW its centre of calculated.
Reply 2
I don't like how they did it, basically the corner of the page has be folded so that now that triangle has twice the area/mass. Instead of doing it like that they have treated it as two separate triangles notice one has a negative mass/area because it doesn't actually exist.
Reply 3
is there a btter /easier way to do it do you think

p.s is that a general rule that centre mass of triangle is 1/3 and centre mass of triangle folded over is 2/3

thanks

p.p.s does the working etc look good from your point of view thanks
Reply 5
investor
is there a btter /easier way to do it do you think


Well its not an easier way of doing it but you can do it this way.

Think of the object as having on the right hand side a 4 by 8 rectangle.
Also on the bottom left side having a 4 by 4 square.
The centre of mass of these two objects should be easy to find.

Now this bit, think of the triangle as being one triangle on top of another triangle.
The mass of one triangle of (4 x 4) / 2 = 8m.
But you got two of these therefore the new mass is 16m.

You should know how to find the centre of mass of a triangle.

Put these info into the table with the mass of the triangle as 16.

Now calculate the mean x and y
Reply 6
thanks but what do they mean by Distance from AB 16/3
Reply 7

this is a bit confusing, i wasnt taught doing it this way and also you have found out the length of the hypotenuese which is more work
Reply 8
investor
thanks but what do they mean by Distance from AB 16/3

im guessing that 16/3 is the centre of mass of tre triangle.

That dotted line makes things more complicated than it actually is.
Reply 9
goku999
this is a bit confusing, i wasnt taught doing it this way and also you have found out the length of the hypotenuese which is more work


Yeah to each and his own, investor just try playing around with it yourself and see what method you prefer. Personally I dont even use the tables I prefer to take moments about a point.
Reply 10
many thanks guys i have just had a go at some questions and your ideas are working great thanks only one prob for now as im off to bed in a mo



how would i find the centre mass of this triangle thanks

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